Investigation of photoconductive effect on Bi2Te3 epitaxial film

Abstract

In this work, we present the results of photoconductivity measurements performed in the temperature range of 12 K–300 K on a 150 nm-thick Bi2Te3 film grown by molecular beam epitaxy on a (111) BaF2 substrate. A transition from negative to positive photoconductivity is found to occur around 125 K. Resistivity and Hall data measured under light and dark conditions qualitatively elucidate the observed phenomena. The Arrhenius plot of recombination times obtained from photoconductivity decay curves measured at different temperatures gives the activation energy associated with the bulk trap level. Using this activation energy as the effective trap potential, we calculated the generation and recombination rates as a function of temperature. The analysis provides a quantitative explanation that predicts the transition effect observed in the experiment. No evidence of contribution from surface states is found from the magnetoresistance curves measured at low temperatures.